grounded to the same point, and both getting their constant power from the same point

As I mentioned, when the empeg and the CD receiver were grounded to the same point (on the same line), I had more noise than when they were grounded to different points (on the same line).

Constant power cannot come from exactly the same point in my case, unless I want to run the CD receiver's constant power line directly to the battery as well. The direct line to the battery is the solution to a voltage dropoff I was having when the empeg and CD receiver were on the same constant power line (using the aforementioned T-Harness).

But yes, the grounding is two different ways at this point. The empeg's ground is connected to a bolt on the frame of the dashboard, whereas the CD receiver's ground is connected to the normal ground wire from the original Honda wiring harness.

And as for wire gauge, I believe the empeg is all 18AWG? My CD receiver is 16AWG all-around. And the direct line to the battery for the empeg's constant line is 12AWG with an in-line fuse near the battery.